The O.W.L. can be super useful in Shadow Fall. It attacks soldiers, hacks terminals to prevent reinforcements, and so forth. Use it often to give yourself an advantage.
Don't fret if you happen to be low on ammo. When you kill enemies, they often drop their weapons. They may be less useful than what you currently have equipped, but a gun is pretty useless without ammo.
Remember to press up on the d-pad to see objectives. It's a lot easier to get lost in Shadow Fall than in past Killzone games.
Experiment with classes in multiplayer. Everyone loves to shoot things, but there may be cases in which a support class proves more useful to the team.
Complete challenges to upgrade your weapons and abilities.
Use your abilities often. There's no point in holding onto a special ability if you're just going to die.
Be a team player. Work with the group and try to succeed in a particular role. It's not always about shooting the other team and racking up kills.

Dark Souls reference
When you first start, look on the walls to find a poster for "Dark Trolls" which features the main character from Dark Souls being chased by a large troll.

Trophy How to unlock
All Flavors (Bronze) Make a kill with all primary weapons as an Insurgent.
Finders Keepers (Bronze) Collect 25 Online Collectibles.
Hacktivist (Bronze) Reach the maximum level for the Hacking Ability.
Kleptomania (Bronze) Reach the maximum level for the Stealing Ability.
Like a Boss (Gold) Finish the campaign in Elite mode.
New Toys! (Silver) Reach the maximum level for the E-Pulse Emitter, Tactical Echo Emitter, and Guard Drone.
Remember Me? (Bronze) Make 25 kills with each one of the Retro weapons.

Secret Trophies

Complete the following tasks to unlock PlayStation 4 trophy rewards.

Trophy How to unlock
New Shadow (Bronze) In 'The Savior', complete the mission without being spotted.
The Savior (Gold) Complete level 'The Savior' and prevent the escalation of a new war.
Violence is the answer? (Bronze) In 'The Savior', kill 20 soldiers and still complete the mission.

Various Trophies

Complete the following tasks to unlock PlayStation 4 trophy rewards.

Trophy How to unlock
Assault (Bronze) Max out any upgradable Assault ability.
Conscientious Killer (Bronze) Complete the campaign on any difficulty without shooting any civilians.
Decorated (Silver) Earn a total of 500 accolades.
Deniable (Bronze) In 'The Shadow', operate without raising an alarm or disabling the security mainframe.
Dominator (Silver) Win a match on every multiplayer map.
Elite Shadow Marshal (Gold) Complete all missions on Hard difficulty.
Gatherer (Bronze) Find 50% of the collectibles in the campaign.
Hero (Platinum) Obtain all Killzone Shadow Fall trophies.
Jack Of All Trades (Gold) Max out all upgradable abilities.
Million Points (Gold) Get a total of 1,000,000 points in multiplayer.
Multiplayer Elite (Gold) Complete 400 challenges.
On Your Way (Silver) Complete 200 challenges.
Outgunned (Silver) In singleplayer, kill 6 Helghast with headshots within a single adrenaline rush.
Outmaneuvered (Bronze) In singleplayer, kill 5 Helghast with gunfire while ziplining.
Outsmarted (Bronze) In singleplayer, get a quadruple kill with a single Frag Grenade.
Scout (Bronze) Max out any upgradable Scout ability.
Shadows Cannot Be Killed (Silver) Complete the campaign on any difficulty without dying.
Support (Bronze) Max out any upgradable Support ability.
The Agent (Bronze) Complete level 'The Agent'.
The Dead (Silver) Complete level 'The Dead'.
The Destroyer (Silver) Complete level 'The Destroyer'.
The Doctor (Bronze) Complete level 'The Doctor'.
The Father (Bronze) Complete level 'The Father'.
The Handler (Bronze) Complete level 'The Handler'.
The Helghast (Bronze) Complete level 'The Helghast'.
The Knowledge (Silver) Find all collectibles in the campaign.
The Patriot (Bronze) Complete level 'The Patriot'.
The Shadow (Bronze) Complete level 'The Shadow'.
Tourist (Bronze) Complete a match on every multiplayer map.
Weapons Specialist (Gold) Unlock all attachments for all weapons.

if you cannot download trainer then go to Chrome/Firefox's settings, specifically to the Privacy settings and simply unchecking the "Enable phishing and malware protection" option.

Some Game Trainers are sometimes reported to be a Virus or Trojan,
the most common is a keylogger called HotKeysHook or the file
has been packed/protected with VMProtect or Themida and
is recognized as Win32/Packed.VMProtect or Win32/Packed.Themida.
In ALL cases this is a FALSE ALARM as NONE
of the Game Trainers @ GGMANIA contain known malicious code!!